Methods and tools for tibial intermedullary revision surgery and associated tibial components

ABSTRACT

IM tibia revision tools include a trial stem extender having multiple notches which serve both as depth witness marks and holders for a stop clip, a collection of different sized tibial templates, each template adapted to receive an angular offset positioning guide, a collection of offset bushings, each bushing each bushing having a different offset distance and each being adapted to cooperate with the trial stem extender and the angular offset positioning guide, a neutral bushing for locating the position of the implant boss relative to the tibia and for reaming the tibia to accept the boss of the implant, a fin punch guide and fin punch for preparing the tibia to receive the keel of the tibial component, and a tool for translating the angular offset measurement to the tibial component. Tibial components according to the invention have three parts: the baseplate portion, the offset portion, and the stem portion. Each portion is provided in a variety of sizes and the portions may be mixed and matched according to the measurements made with the tools described above. Methods for using the tools and the tibial components are also disclosed.

This application is related to co-owned, co-pending Ser. No. 09/049,708,filed Mar. 28, 1998, entitled Methods and Tools for FemoralIntermedullary Revision Surgery, the complete disclosure of which ishereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to methods and tools used in knee arthroplasty.More particularly, the invention relates to methods and tools used inrevision surgery where an artificial tibial component is removed andreplaced. The invention also relates to improved tibial components.

2. Brief Description Of The Prior Art

Total knee arthroplasty involves the replacement of portions of thepatellar, femur and tibia with artificial components. In particular, aproximal portion of the tibia and a distal portion of the femur are cutaway (resected) and replaced with artificial components. As used herein,when referring to bones or other body parts, the term "proximal" meansclosest to the heart and the term "distal" means more distant from theheart. When referring to tools and instruments, the term "proximal"means closest to the practitioner and the term "distal" means moredistant from the practitioner.

There are several types of knee prostheses known in the art. One type issometimes referred to as a "resurfacing type". In these prostheses, thearticular surface of the distal femur and proximal tibia are"resurfaced" with respective metal and plastic condylar-type articularbearing components. These knee prostheses provide adequate rotationaland translational freedom and require minimal bone resection toaccommodate the components within the boundaries of the available jointspace.

The femoral component is a metallic alloy construction (cobalt-chromealloy or 6A14V titanium alloy) and provides medial and lateral condylarbearing surfaces of multi-radius design of similar shape and geometry asthe natural distal femur or femoral-side of the knee joint.

The tibial component usually includes a distal metal base component anda proximal interlocking plastic, e.g. UHMWPE (ultra high molecularweight polyethylene), component or insert. The plastic tibial plateaubearing surfaces are of concave multi-radius geometry to more or lessmatch the articular geometry of the mating femoral condyles. Both thefemoral and tibial components are usually provided with intermedullary(IM) stem options.

After preparing the distal surface of the femur and the proximal surfaceof the tibia, an opening is made into the medullary canal of the femur,and an opening is made into the medullary canal of tibia. The interiorsurface and the IM stem of the femoral component are usually coveredwith a polymeric cement and the IM stem is inserted into the medullarycanal of the femur until the interior surface of the femoral componentmeets the distal surface of the femur. The tibial component is similarlyusually cemented to the proximal surface and medullary canal of thetibia.

Occasionally, the components are press fit without the use of cement.The use of cement has advantages and disadvantages. Press fit componentsrely on bone quality to obtain good fixation. Sometimes it is impossibleto obtain good fixation with a press fit component and sometimes a pressfit component will fail early because of failure of successfulbiological ingrowth. Cement assures good fixation but puts strain alongthe component stem. In addition, as described below, cement complicatesthe removal of a failed component.

Often, due to normal wear over time, the prosthetic knee must bereplaced via a procedure known as revision surgery. When the primarycemented prosthetic is removed, the proximal surface of the tibia andthe distal surface of the femur typically exhibit cavernous defects.Absent the use of bone graft, the proximal surface of the tibia and thedistal surface of the femur must be carefully resected to removecavernous defects before a replacement knee can be installed.

In addition, the intramedullary (IM) canals must be broached or reamedto remove any remaining cement or cavernous defects existing in thecanals before a replacement knee can be installed.

According to the state of the art, after the primary prosthetic isremoved, the proximal tibia is resected with a lateral template. Themedullary canal is reamed and the reamer is tapped in place with amallet. A proximal resection guide is attached to the reamer andproximal resection is completed via slots in the guide. Preparation ofthe distal femur is described in the above referenced relatedapplication.

The defects in the tibia are measured and the cutting guide is moveddown 6 to 10 mm. A flat cut from anterior to posterior is made. A tibialtemplate is attached to the reamer and reference marks are typically inpen. A flat cut and sagittal cut are made relative to the referencemarks. Another template is attached to the reamer and anterior andposterior holes are drilled for securing a wedge resection guide. Awedge cut is then made. The template is replaced and aligned with themarks. A revision mask punch guide is attached to the template and arevision box chisel is used to prepare for a stem.

Those skilled in the art will appreciate that revision surgery isdifficult because (1) the type and location of cavernous defects make itdifficult to match the exterior surfaces of the tibia and femur to theinterior surfaces of the prosthetic, (2) the femur and tibia must beresected with reference to the IM canal, and (3) the use of multipletemplates and guides during the course of the procedure makes it verydifficult to keep all the cuts in proper alignment relative to the IMcanal.

In particular, with respect to the tibia, resection of the proximaltibia results in the creation of a tibial plateau in which the IM canalis no longer centrally located. If a normal tibial component isinstalled, portions of the tibial component will overhang the resectedtibial plateau.

In order to compensate for this problem, it is known in the art toprovide tibial components with offset IM stems. However, the relativelocation of the IM canal relative to the perimeter of the tibial plateaumay be offset in any direction, anterior, posterior, medial, or lateral,depending on the individual bone. It is impossible or at leastimpractical to provide an offset stem tibial component for everypossible variation in the relative location of the IM canal.

Moreover, it is difficult to estimate the offset of the IM canal inorder to choose an appropriate offset tibial component.

According to the state of the art, offset tibial components are selectedby trial and error, a tedious procedure which prolongs surgery. Forexample, as shown in FIG. 1, a relatively symmetrical tibial plateau 10exhibits the IM canal 12 in a central location. After resection of thetibial plateau, the location of the IM canal may be located off centeras shown in FIGS. 2 and 3 where canals 12' and 12" are seen to belocated off center relative to the plateaus 10' and 10" respectively.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide methods and toolsfor performing IM revision surgery.

It is also an object of the invention to provide tools for IM revisionsurgery which maintain proper alignment with the IM canal while multipleresection cuts are made, tools for determining the offset location ofthe IM canal relative to the tibial plateau, tools which enhance theaccuracy of IM revision surgery and enhance the stability of therevision implant.

It is another object of the invention to provide methods for performingIM revision surgery in which a minimum number of tools are used.

The methods and tools of the invention provide accurate location of bonecuts so that the revision prosthetic is correctly oriented relative theIM canal and the bone cuts. Moreover, the tools and methods provideaccurate measurements for use in selecting the appropriate tibialcomponent and for adjusting the angular offset of the tibial componentaccording to the measurements. Additional objects and advantages of theinvention will become apparent to those skilled in the art uponreference to the detailed description taken in conjunction with theprovided figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic plan view of a relatively symmetrical tibialplateau;

FIG. 2 is a view similar to FIG. 1 showing a slightly offset IM canal;

FIG. 3 is a view similar to FIG. 1 showing a more dramatically offset IMcanal;

FIG. 4 is a perspective view of the resection guide tower attached tothe tool stem;

FIG. 5 is a perspective view of the impactor/extractor;

FIG. 6 is a broken perspective transparent view of the guide towerinstalled in the IM canal of the tibia;

FIG. 7 is a view similar to FIG. 6 with the optional collar attached tothe tool stem;

FIG. 8 is a broken perspective view of the cutting block attached to thetool stem;

FIG. 9 is a view similar to FIG. 8 showing the optional extra medullaryreferencing tool attached to the cutting block;

FIG. 10 is a broken perspective transparent view of a trial stemextender and trial stem inserted into the IM canal of the tibia;

FIG. 11 is a broken perspective view showing the tibial template andoffset positioning guide placed over the trial stem on the tibialplateau;

FIG. 12 is a view similar to FIG. 11 showing the 4 mm offset bushinginstalled in the angular offset positioning guide;

FIG. 13 is a perspective view of the 4 mm, 6 mm. and 8 mm offsetbushings;

FIG. 14 is view similar to FIG. 12 showing the optional stop clipattached to the trial stem extender;

FIG. 15 is an enlarged broken perspective view of the 4 mm offsetbushing installed in the angular offset positioning guide indicating anangular offset of 320 degrees and showing the template pinned to thetibia;

FIG. 16 is a view similar to FIG. 15 showing the 4 mm offset bushingremoved and the boss reamer bushing in its place;

FIG. 17 is a view similar to FIG. 16 showing the boss reamer (oroptionally an offset boss reamer) in the reamer bushing;

FIG. 18 is a view similar to FIG. 17 with the reamer, bushing, andangular offset guide removed from the template and with the fin punchguide and fin punch in their place;

FIG. 19 is an exploded perspective view of a tibial component accordingto the invention;

FIG. 20 is an exploded perspective view of the component stem andwrench;

FIG. 21 is an exploded perspective view of the tibial component and thetool for translating the angular offset to it; and

FIG. 22 is a sectional view of the component and tool of FIG. 21.

DETAILED DESCRIPTION

An illustrative embodiment of the invention is set forth hereinafter.The illustrative embodiment makes reference to specific measurements fortool diameters, cut depths, etc., which are intended only to give thoseskilled in the art an appreciation for the operating principals of theinvention without any intent of limiting the spirt or scope thereof. Itis applicants' intention that the invention only be limited by theappended claims and not any of the exemplary measurements set forth inthe illustrative embodiment of the invention.

According to the methods of the invention, the previous tibial componentis removed from the tibia and the IM canal of the tibia is reamed asdescribed in the parent application hereto.

Referring now to FIG. 4, after the tibial IM canal is prepared, based onthe diameter and reaming depth of the last IM reamer used, anappropriate tool stem 20 is chosen for attachment to the resection guidetower 22. The tower 22 has a boss 24 with a pair of surface grooves 26,a stem 28 with a pair of surface grooves 30, and an upstanding shaft 32therebetween. The boss 24 has interior threads (not shown) and the stem20 is provided with engaging exterior threads (not shown). According toone embodiment of the invention, the boss 24 has a diameter of 15 mm andseveral stems 20 of different diameter are provided for attachment tothe tower 22.

Turning now to FIGS. 5 and 6, the resection guide tower 22 with theattached tool stem 20 is installed in the IM canal 34 of the tibia 36with the aid of the impactor/extractor 40. The tool 40 has a proximalhandle 42, a distal coupling 44, and a sliding mass 46. The coupling 44has a slot 44a which is dimensioned to receive the stem 28 of the tower22, and a pair of distal shoulders 44b which are dimensioned to fit intothe slots 30 of the stem 28. A spring loaded latch 44c is locatedadjacent to the slot 44a.

The tool 40 is removably attached to the tower 22. The stem 20 of thetower is then inserted into the IM canal 34 and the sliding mass 46 ofthe tool 40 is slid distally. The force of the accelerated mass 46impacts the coupling 44 and drives the stem 20 of the tower 22 into theIM canal 34. If necessary, the mass is slid several times until the stem22 is fully inserted into the IM canal 34. After the tower is installed,as shown in FIG. 6 the impactor/extractor tool is uncoupled from thetower.

In situations where the IM canal opening is enlarged and does notprovide adequate support or a good reference point to seat the tower, atibial collar 48, shown in FIG. 7, is attached to the boss 24 byengaging the grooves 26. The tibial collar 48 is shaped and dimensionedto cover the tibial plateau 37. In addition to stabilizing the tower 22,the collar 48 aids in preliminary sizing of the tibial plateau 37.

Once the tower 22 is properly installed, a tibial cutting block 50(which is provided in separate left and right versions) is attached tothe upstanding shaft 32 of tower 22 as shown in FIGS. 8 and 9 by meansof a cam lock 52 and the two 1/8" drill bits 54, 56 inserted into holes58, 60. If desired, as shown in FIG. 9, a handle 70 and rod 72 areattached to the cutting block 50 so that an optional visual EM alignmentinspection can be made.

With the cutting block 50 so secured, a typical 2 mm clean-up cut can bemade using the proximal surface 62 of the cutting block as a guide.According to a preferred embodiment of the invention, three degrees ofposterior slope is built into the cutting block and this is why separateleft and right cutting blocks are provided. Slots 64, 66 are providedfor optional wedge cuts. After the clean-up cut and wedge cuts (ifdesired) are made, the cutting block 50 and the tower 22 are removedfrom the tibia 36. The removal of the cutting block and tower iseffected with the aid of the impactor extractor 40.

Turning now to FIG. 10, after the cutting block and tower are removedfrom the tibia, a trial stem extender 74 is attached to the trial stem20 (or another trial stem of the same size). The trial stem extender hasa proximal coupling 76 for coupling to the impactor/extractor, and threepairs of circumferential grooves 78, 80, 82 which serve as witness marksand receivers for a stop clip (described below with reference to FIG.14). The witness marks are useful in determining the length of the stemportion of the tibial component implant.

With reference to FIG. 11, with the trial stem and extender 74 in place,an appropriately sized tibial template 84 is selected. The templates 84are provided in a variety of sizes to correspond to different sizedtibial plateaus 37. The size of the template 84 chosen may be based onthe size of the collar 48 chosen above. According to the invention,therefore, several different sized templates 84 are provided. Eachtemplate 84 has a central circular opening 86 of standard size forreceiving the offset positioning guide 88. The offset positioning guide88 is a generally cylindrical member with a plurality of circumferentialmarkings 90 which indicate angles between 0 degrees and 360 degrees. Forclarity, the angle values are not shown in the drawing, except for FIG.15 which only shows one angle value.

In the presently preferred embodiment, the angle markings 90 are spaced5 degrees apart (i.e. there are seventy-two markings about the perimeterof the offset positioning guide 88). As suggested by FIG. 15, in thepreferred embodiment, the angle values are provided for every otherangle marking 90. The tibial template 84 is also provided with aplurality of pin receiving holes 92 (described below with reference toFIG. 15), and a coupling 94 for an optional EM alignment guide (like theguide 70, 72 shown in FIG. 9).

Turning now to FIGS. 12 and 13, the tools of the illustrative embodimentof invention include three offset bushings 96, 98, 100. Each bushing isa substantially cylindrical member which is dimensioned to fit withinthe cylindrical offset positioning guide 88 as shown in FIG. 12.

Each bushing 96, 98, 100 is provided with a circumferential indicator96a, 98a, 100a and a throughbore 96b, 98b, 100b which is designed toreceive the trial stem extender 74. According to the invention, thethroughbores are not centrally located relative to the center of thecylindrical bushings. Each bushing 96, 98, 100 has a throughbore 96b,98b, 100b which is offset a different amount from the center of thecylindrical bushing.

According to the presently preferred embodiment, bushing 96 has a 4 mmoffset, bushing 98 has a 6 mm offset, and bushing 100 has an 8 mmoffset. The circumferential indicators 96a, 98a, 100a are preferablylocated on the same radius along which the throughbores 96b, 98b, 100bare offset.

As shown in FIGS. 12 and 14, an appropriate offset bushing, e.g. 96, ischosen and fitted into the cylindrical offset positioning guide 88 withthe trial stem extender 74 extending through the throughbore, e.g. 96b.The appropriate bushing is chosen by visual assessment or by trial anderror. optionally, if the trial stem and extender 74 are unstable in theIM canal, a stop clip 102 may be attached to one of the grooves in theextender 74 as shown in FIG. 14.

With the extender 74, template 84, cylindrical offset positioning guide88, and bushing 96 assembled as shown, the bushing is rotated relativeto the cylindrical offset positioning guide 88 until the template 84assumes a position relative to the tibial plateau 37 where there isminimum or no overhang. When the optimal (best) position is obtained,the template 84 is pinned to the tibia 36, for example with 1/8" drillpins (or headed nails) 104 through the pin receiving holes 92. The angleindicated by the indicia 96a and 90 is noted before the bushing 96 andstem with extender 74 are removed.

According to the invention, a neutral (boss reaming) bushing 106 isprovided. The neutral bushing 106 is substantially the same size andshape as the offset bushings 96, 98, 100, but has a centrally locatedthroughbore 107 and no radial indicia. The purpose of the neutralbushing is to act as a guide for reaming a hole in the center of thetibial plateau 37 for receipt of the boss portion of the tibial implant.Those skilled in the art will appreciate from the foregoing that thelocation of the center of the "boss hole" will be offset from the tibialIM in the angular direction indicated by the indicators 90, 96a at thestep shown in FIG. 15 by an amount equal to the offset amount of thebushing 96 (e.g. 4 mm).

Turning now to FIG. 17, with the template 84 pinned to the tibia 36 bydrill pins 104 and with the neutral bushing 106 inserted in the offsetpositioning guide 88, a boss reamer 110 (or optionaly an offset bossreamer) is inserted into the throughbore 107 of the neutral bushing 106.The illustrative boss reamer 110 shown in FIG. 17 is 15 mm in diameterand has two depth markings shown, 112 and 114. All of the tibialbaseplates according to the illustrative embodiment of the inventionhave a 15 mm diameter boss, but different baseplates have bosses withdifferent lengths.

Having chosen the appropriately sized template 84, the practitioner willknow which tibial baseplate will be used in the implant and will knowhow deep to ream the hole for the boss of the baseplate. Thus, at thisstage of the method of the invention, the practitioner uses the reamer110 to ream to the appropriate depth indicated by the appropriate depthmark 112 or 114.

After reaming for the baseplate boss, the tibia is punched to make spacefor the baseplate fins or "keel". The boss reamer 110, the neutralbushing 106, and the offset positioning guide 88 are removed and thetemplate 84 is left pinned to the tibia. The fin punch guide 120, shownin FIG. 18, is attached to the template 84. The guide 120 has left andright fin guides 122, 124 and a central boss guide 126. The fin punch130 has left and right fins 132, 134 and a central boss 136.

The punch 130 is inserted into the punch guide 120 as shown in FIG. 18with the central boss 136 entering the central boss guide 126 and theleft and right fins 132, 134 entering the left and right fin guides 122,124. With the punch 130 in place, it is struck with a mallet (orattached to the impactor/extractor), driven into the tibial plateau, andthen removed. Optionally, if a wedge cut had not been performed at thestart (i.e. during the steps described with reference to FIGS. 8 and 9),a wedge cutting guide (not shown) may be attached to the coupling 94 ofthe template 84 and a wedge cut performed at this stage of theprocedure.

All of the apparatus are now removed from the tibia and the tibialcomponent is prepared for implant into the tibia. As mentioned above andas shown in FIG. 19, the tibial component 140 includes the baseplateportion 142, the offset portion 144, and the stem portion 146. It willbe appreciated that the tibial component 140 is shown inverted andexploded in FIG. 19 to illustrate the manner in which it is assembledrather than the manner in which it is implanted.

The baseplate 142 can be seen to have a central boss 148 and a pair offins 150, 152. The offset portion 144 has a male coupling 154 whichengages the boss 148, and a female coupling 156 which mates with thestem portion 146. The axes of the couplings 154 and 156 are offset by acertain amount, e.g. 4 mm, 6 mm, or 8 mm, corresponding to the offsetbushings 96, 98, 100 shown in FIG. 13 and described above. Between themale coupling 154 and the female coupling 156 is a tightening nut 155which is used to lock the angular position of the two couplings relativeto each other as described in detail below with reference to FIGS. 21and 22.

According to the presently preferred embodiment, the stem 146 has a malecoupling 158 at its proximal end and a trifurcated distal end 160. Thefluted stem 146 is preferably coupled to the offset component 144 withthe air of a trifluted wrench 162 which is shown in FIG. 20.

Turning now to FIG. 21, the offset portion 144 is fixedly attached tothe stem portion 146 and loosely coupled to the baseplate portion 142.The baseplate portion 142 is placed in the base 164 of an angularadjustment tool 166. A turntable portion 168 of the tool 166 is placedover the stem portion 146, the offset portion 144 and tightening nut155, engaging both the base 164 and baseplate portion 142. The turntable168 has a locking knob 170 and an angle indicator/wrench key 172.

With the tool 166 assembled about the tibial component 140 as shown inFIG. 22, the angle indicator/wrench key 172 is turned until it indicatesthe angle previously noted at the step described with reference to FIG.15. When the angle has been so "dialed in", the offset portion 144 istightened to the baseplate 142 using the wrench 174 (FIG. 21) on thetightening nut 155. The tibial component is now assembled and ready forimplantation. Optionally, if wedge cuts had been made, one or morewedges may be added to the bottom of the baseplate 142 either before orafter the assembly of the baseplate, stem, and offset portion.

There have been described and illustrated herein methods and tools forIM revision surgery involving tibial components. While particularembodiments of the invention have been described, it is not intendedthat the invention be limited thereto, as it is intended that theinvention be as broad in scope as the art will allow and that thespecification be read likewLse. It will therefore be appreciated bythose skilled in the art that yet other modifications could be made tothe provided invention without deviating from its spirit and scope as soclaimed.

What is claimed is:
 1. A positioning template system for determining therelative location of the IM canal relative to the perimeter of thetibial plateau with the aid of a trial stem inserted in the IM canal,said system comprising:(a) a template approximating the size and shapeof a tibial plateau; (b) angular indication means coupled to saidtemplate for indicating an angle about the center of said template; (c)offset bushing means rotatably coupled to said angular indication means,said offset bushing means having positional indicia and a throughboredimensioned to fit over the trial stem, said throughbore being offsetfrom the center of said bushing means; wherein rotation of said bushingrelative to said angular indication means causes movement of saidtemplate relative to said tibial plateau and said positional indiciawith said angular indication means indicating the approximate angularposition of the center of said template relative to the IM canal.
 2. Asystem according to claim 1 wherein said template comprises a pluralityof different sized templates.
 3. A system according to claim 2 whereinsaid angular indication means is adapted to be removably coupled to eachof said plurality of different sized templates.
 4. A system according toclaim 3 wherein said offset bushing means includes a plurality of offsetbushing means, each offset bushing means have a throughbore which isoffset by a different amount from the center of the offset bushingmeans, and each offset bushing means adapted to be removablyrotationally coupled to said angular indication means.
 5. A systemaccording to claim 1 wherein said template includes means for fixingsaid template to the tibia.
 6. A system according to claim 5 furthercomprising neutral bushing means adapted to be removably coupled to saidtemplate, said neutral bushing means having a throughbore located at thecenter of said template.
 7. A system according to claim 6 wherein saidoffset bushing means is adapted to be removably rotationally coupled tosaid angular indication means and said neutral bushing means is adaptedto be removably rotationally coupled to said angular indication means.8. A system according to claim 1 further comprising a fin punch guidecoupled to said template and adapted to receive a fin punch.
 9. A systemaccording to claim 1 wherein said angular indication means is adapted tobe removably coupled to said template and said fin punch guide isadapted to be removably coupled to said template.
 10. A method fordetermining the relative location of the IM canal relative to theperimeter of the tibial plateau with the aid of a trial stem inserted inthe IM canal, said method comprising the steps of:(a) placing a templateapproximating the size and shape of a tibial plateau on the tibialplateau; (b) coupling angular indication means to the template forindicating an angle about the center of said template; (c) placingoffset bushing means having positional indicia and an offset throughboreover the trial stem and into the angular indication means; (d) rotatingthe bushing relative to the angular indication means causing movement ofthe template relative to said tibial plateau; (e) stopping rotation whenthe position of the template is located over the tibial plateau withlittle or no overhang; (f) noting the location of the positional indiciarelative to the angular indication means.
 11. A method according toclaim 10 wherein said step of placing a template includes selecting oneof a plurality of different sized templates.
 12. A method according toclaim 11 wherein said step of placing offset bushing means includesselecting one of a plurality of offset bushing means, each offsetbushing means having a throughbore which is offset by a different amountfrom the center of the offset bushing means.
 13. A method according toclaim 10 further comprising the step of removably fixing the template tothe tibia after noting the location.
 14. A method according to claim 13further comprising the steps of:(a) removing the offset bushing meansfrom the angular indication means; (b) removing the trial stem from thetibial IM canal; (c) inserting neutral bushing means having a centralthroughbore into the angular indication means; and (d) reaming a holefor an implant boss using the neutral bushing means as a guide.
 15. Amethod according to claim 13 further comprising the steps of:(a)removing the offset bushing means from the angular indication means; (b)removing the trial stem from the tibial IM canal; (c) attaching a finpunch guide to the template; (d) inserting a fin punch into the guide;and (e) driving the fin punch into the tibia.
 16. A method according toclaim 15 further comprising the step of removing the angular indicationmeans prior to attaching a fin punch guide to the template.
 17. A methodaccording to claim 10 and for translating the determined location to atibial component having a baseplate and a stem where the stem is offsetfrom the center of the baseplate, said method further comprising thesteps of:(a) attaching the baseplate of the tibial component to a baseportion of an adjustment tool; (b) attaching a turntable portion of theadjustment tool to the stem of the tibial component and to the baseportion of the tool; (c) rotating the turntable until angular indicationmeans on the tool indicate substantially the same noted location of thepositional indicia relative to the angular indication means.
 18. A setof IM tibia revision tools, comprising:(a) a trial stem extender havingat least one notch which serves as a depth witness mark; (c) a pluralityof different sized tibial templates each template adapted to receive anangular offset positioning guide; (d) an angular offset positioningguide; (e) a plurality of offset bushings, each bushing having adifferent offset distance and each being adapted to cooperate with saidtrial stem extender and said angular offset positioning guide toindicate the approximate angular offset position measurement of thecenter of said given template relative to the IM canal; (f) a neutralbushing for locating the position of the implant boss relative to thetibia and for reaming the tibia to accept the boss of the implant; (g) afin punch guide and fin punch for preparing the tibia to receive thekeel of the tibial component; and (h) means for translating said angularoffset position measurement to the tibial component.
 19. A set ofinstruments as set forth in claim 18 further comprising an instrumentstabilizing stop clip and further wherein said at least one notch onsaid trial stem extender serves as a holder for said stop clip.
 20. Aset of instruments for use in revision knee surgery to determine theoffset location of the tibial IM canal relative to the perimeter of thetibial plateau and translate the determined offset location to the stemportion of a tibial component, comprising:(a) an impactor-extractor witha distal coupling for attaching to other tools which are inserted intoand removed from the IM canal; (b) a resection guide tower to which acutting block may be attached, said guide tower including a notch whichserves as both a witness mark and a holder for a tibial collar; (c) aplurality of different sized trial stems attachable to said guide tower;(d) a plurality of different sized tibial collars; (e) right and leftcutting blocks, each attachable to said guide tower, for resecting theproximal tibia; (f) a trial stem extender having at least one notchwhich serve as a depth witness mark and holder for an instrumentstabilizing stop clip; (g) an instrument stabilizing stop clip; (h) aplurality of different sized tibial templates, each template adapted toreceive an angular offset positioning guide; (i) an angular offsetpositioning guide; (j) a plurality of offset bushings, each bushinghaving a different offset distance and each being adapted to cooperatewith said trial stem extender and said angular offset positioning guideto indicate the approximate angular offset position measurement of thecenter of a given template relative to the IM canal; (k) a neutralbushing for locating the position of an implant boss relative to thetibia and for reaming the tibia to accept the boss of the implant; (l) afin punch guide and fin punch for preparing the tibia to receive thekeel of a tibial component; and (k) means for translating said angularoffset position measurement to the tibial component.
 21. Apparatus asset forth in claim 20 wherein each of said right and left cutting blocksfurther comprise a clamp from removably attaching a given cutting blockto said guide tower.
 22. A method for performing tibial IM revisionsurgery, comprising the steps of:(a) removing the primary tibialcomponent; (b) reaming the tibial IM canal to the extent necessary toreceive a trial stem; (c) selecting a trial stem for insertion into theIM canal; (d) attaching a trial stem extender to said trial stem, saidtrial stem extender having at least one depth marking thereon; (e)inserting said trial stem into the tibial IM canal noting the depthmarkings on the attached trial stem extender; (f) selecting a tibialtemplate; (g) attaching an angular offset positioning guide to theselected template, and (h) selecting an offset bushing and placing theselected offset bushing onto said trial stem extender, engaging saidpositioning guide with said bushing and rotating said bushing until theselected tibial template is located in a position relative to the tibialplateau where there is a minimum of overhang.
 23. A method as set forthin claim 22 further comprising the steps of:(a) attaching a guide towerto the trial stem; (b) inserting the trial stem with attached guidetower into the tibial IM canal; (c) attaching an impactor/extractor tothe proximal end of said guide tower; (d) impacting said tibial stem andsaid guide tower combination into the IM canal; (e) optionally attachingan instrument stabilizing stop to the trial stem; (f) attaching acutting block to said guide tower; (g) resecting the proximal tibia; (h)removing said cutting block from said guide tower; and (i) removing saidguide tower and said trial stem utilizing said impactor/extractor.
 24. Amethod as set forth in claim 22 further comprising the steps of:(a)pinning said selected template to the tibia; (b) recording the angleindicated by the bushing on the positioning guide; and (c) removing theoffset bushing and the trial stem.
 25. A method as set forth in claim 24further comprising the steps of:(a) placing a boss reaming bushing insaid positioning guide; (b) reaming the tibia to receive the implantboss; and (c) removing the positioning guide from the template.
 26. Amethod as set forth in claim 25 further comprising the steps of:(a)attaching the fin punch guide to the template; (b) punching the tibiawith the fin punch; (c) choosing a baseplate, offset and stem for theimplant; (d) assembling the implant; (e) translating said angular offsetposition measurement to the assembled implant; and (f) installing theimplant.